1. Field of the Invention
The present invention relates to a support table for supporting a plate-like body such as a wafer in a vacuum apparatus, for example, a plasma etching apparatus, and a processing apparatus using the table.
2. Description of the Related Art
In a plasma etching apparatus, a support table called a "susceptor" is used to support a wafer. Since the temperature of the wafer is increased by a plasma during etching, the susceptor incorporates a temperature adjusting mechanism for cooling the wafer at a predetermined temperature. The susceptor acts as a lower electrode of the plasma etching apparatus.
In recent years, since the diameter of wafers become large and the kind of diameters of wafers are increased in accordance with increasing bypass of wafers, susceptors corresponding to the respective wafer sizes must be provided. Published Unexamined Japanese Patent Application No. 59-115521 discloses an apparatus which can use susceptors corresponding to various types of wafers.
In addition, since damage is caused on the surface of a wafer support table for use in, for example, plasma etching, the support table must be replaced as a consumable. If the support table has, e.g., for example, an electrostatic chuck sheet, the electrostatic chuck must also be replaced.
For the above reasons, a demand has arisen for a support table which can be split into two portions, that is, a stationary portion and a removable portion so that replacement can be performed by only removing the removable portion in accordance with the size of a wafer or when the surface is damaged. That is, when the support table is split into two portions, while the stationary portion having a temperature adjusting function is constantly set, a plurality of types of removable portions can be prepared in accordance with the sizes of wafers, thereby processing wafers of various sizes. In addition, since only the removable portion need be removed in the replacement of the support table surface or the electrostatic chuck, the replacement can be easily performed.
When the above split structure is adopted in the support table, however, since the removable portion and the stationary portion are always joined with each other with a gap formed therebetween or dust sandwiched therebetween, a heat conduction characteristic between the stationary and removable portions is degraded. Therefore, the temperature of an object to be processed cannot be efficiently adjusted. Especially when the support table is used in a vacuum processing apparatus such as an etching apparatus, a portion defined between the stationary and removable portions is in a vacuum state. Therefore, no heat conduction is caused by a gas, but only solid contact heat conduction near boltfastened portions between the two portions can be expected. In this case, since the bolt connection portion is present in a peripheral portion of the support table, no effective heat conduction can be expected in a central portion of the table. Therefore, it is very difficult to perform uniform temperature adjustment of a wafer.